This invention relates to a device for dispersing liquid into vapor and to a process for dispersing or spraying liquid.
A device for dispersing a liquid such as, for example, air freshening device in which there is a slow release of vapor into air from a liquid is well known in the art. See, e.g., U.S. Pat. Nos. 2,942,090; 3,780,260; 4,084,079; and 6,478,440. However, current devices rely on evaporation of the liquid from a wick and have the disadvantages of depleting the liquid at an uneven rate and composition, evaporating the more volatile components of the liquid mixture faster and thereby leaving a disproportionately different composition in the liquid from the original composition.
Electrostatic devices for spraying liquids into the air are also well known in the art. See, e.g., U.S. Pat. No. 5,810,265; and EP patent application 0 486 198. In such devices, liquid delivered to a point of high electric potential is drawn out by electrostatic forces into ligaments which break up into fine electrically charged droplets. The liquid is typically delivered to the point of high electric potential by a non-mechanical means such as capillary rise in a small diameter tube or by wicking. Under conditions in which mass transfer by formation of liquid droplets far exceeds the evaporation rate, electrostatic spray devices offer the potential of substantially maintaining a constant liquid composition during the course of dispersing the liquid.
However, the known electrostatic spraying devices that rely on passive delivery of liquid from the reservoir to the high voltage region (by capillary rise or wicking) lack ruggedness. Furthermore, the voltages required for producing electrostatic spraying using the known devices are above 5,000 V and frequently above 10,000 V. At these voltages in air, it is difficult not to produce a Townsend or glow discharge.
Therefore, it is highly desirable to derive a mass transfer device that disperses liquid into a vapor while substantially maintaining the liquid composition at the original composition over the useful life of the device. An advantage of the invention is the range of composition of the liquid to be dispensed can be extended and the composition is not substantially altered for a prolonged period of time.
Accordingly, the invention comprises a device that can be used as an electrospray device for dispersing liquids into a vapor phase that comprises a container, a capillary device, and a housing. The container has an open end that is connected to the capillary device and comprises a liquid. The capillary device comprises a substantially tubular member having a first end and an opposing end; the first end is secured to the open end of the container; the opposing end has extended therethrough a substantially tubular capillary structure having a capillary tip; the capillary structure is within and coaxially aligned with the substantially tubular member; and the capillary structure is in fluid communication with the liquid in the container. The housing comprises a first end having an opening attached thereon said container, a second end opposing said first end, a first wall having attached thereon a low voltage supplier, a second wall having attached thereon a high voltage converter, a high voltage contact, a counter electrode, optionally a heat and/or lighting source, and further optionally a wicking material. The capillary device is coaxial with the first wall and the second wall. Optionally, the housing may contain control circuitry to turn the high voltage supply on/off or to regulate the high voltage.
Also provided is a process for dispensing a liquid in which the process comprises attaching a capillary device to a container to produce a capillary-container, attaching the capillary-container to a housing, and applying an electrical current to the housing wherein the container, capillary device, and housing can be the same as those disclosed above.